1. Field of the Invention
This invention relates generally to a discrete particle counter employing a uniform beam of collimated light, and more particularly, to a seed monitor for counting seeds dispensed by a seed planter through a plurality of seed tubes. The seed monitor includes a planter master unit having one or more planter counting units connected to the planter master, each associated with a different seed tube.
A problem associated with seed monitoring using light (herein, the term light refers to visible, infrared and ultraviolet radiation) is the severe dust and dirt associated with the planting process. Cleaning of the optical components is not considered a viable option because of the large number of seed tubes on modern planters. This is because the effects of any single cleaning might be short-lived, resulting from the extremely dusty environment within the seed tube during a seeding operation. Also, because cleaning would probably need to occur when the seed tube was not in use, cleaning would decrease the availability of the planting equipment during a planting season.
Another problem associated with seed monitoring using light is the detection and accurate counting of multiple seeds that pass simultaneously through the sensing area of the seed tube, either individually or as clumps of seeds.
2. Discussion of the Prior Art
As is well understood, it is important to monitor the quantity of seeds that are being planted into a planting row, especially in a high capacity agricultural environment such as a farm where the seeds are corn seeds, soy bean seeds and the like. Planting too many seeds causes the resulting plant product to be too closely spaced together to allow for proper plant growth, thus affecting the crop yield. Planting too few seeds reduces the effective use of the planting area. For high output planting, industrial seed planters have been devised to plant a high volume of seeds relatively quickly. To ensure that the proper number of seeds are planted by the seed planters, a seed monitoring system is generally provided that counts the seeds as they are dispensed through seed tubes associated with the planter. A typical planter will have many seed tubes for planting a multitude of planting rows simultaneously.
One type of seed monitoring system incorporates optical devices that generate an optical beam directed across the seed tubes, and optical sensors that are sensitive to the loss of light intensity caused by seeds interfering with the optical beam. An electrical counting circuit monitors the occurrences of loss of light intensity to provide a count of the seeds. Various optical seed monitoring systems of this type are disclosed in U.S. Pat. Nos. 3,974,377 issued to Steffen; 4,555,624 issued to Steffen, and 4,163,507 issued to Bell.
These and other optical seed monitoring systems have been inaccurate for various reasons. One inaccuracy results from spatial nonuniformity of the optical beam that senses the seeds. Because of spatial nonuniformity, the intensity of an optical beam varies, depending upon the location within the optical beam. Therefore, the ability of the optical sensor to detect the interruption of the optical beam by the seeds varies depending on the location of the seeds within the beam. Consequently, the optical sensor may not adequately detect seeds dropped through certain locations in the seed tube.
One prior art seed monitoring system has attempted to address spatial nonuniformity of the optical beam of a seed sensor by proposing an optical device that generates a trapezoidal cross-section optical beam. However, the trapezoidal cross-section creates an undesirable spatial restriction for groups of seeds as they are dropped through the seed tube. U.S. Pat. No. 4,634,855 issued to Friend et al. also discloses an attempt to create an optical beam of high uniformity. However, this proposed solution is of such a complexity that the feasibility for commercial success is limited.
Another drawback of the known optical seed monitoring systems occurs when the seed sensors are associated with circuitry that counts pulses when the optical beam is interrupted by the seed. This may result in a count inaccuracy because a plurality of seeds may simultaneously traverse the optical beam and be counted as a single seed. A related problem is that the accuracy of the known optical monitoring systems tend to deteriorate with increasing planting speed, with higher seed populations per acre, and with small grains and seeds. These optical systems may be incapable of sufficiently rapid response to reliably count each seed.
Still another drawback of the known optical seed monitoring systems is the complexity, cost, and stocking requirements of their wiring components. The wiring harnesses of the seed tube monitors tend to each be connected to the planter master unit, and thus are unnecessarily complex and ill-suited to a planting operation that monitors less than a full system complement of seed tubes. This results in unneeded expense in stocking wiring components of different lengths as well as a waste of money for an operator who chooses to use fewer seed monitoring units than seed tubes.
What is needed is an optical seed monitoring system that effectively counts each dispensed seed, even at high planting rates, and does not suffer from the drawbacks as discussed above. It is therefore an object of the present invention to provide an optical seed counter capable of counting individual seeds at high seed planting rates, even after long-term accumulation of dust and dirt within the seed planting tubes.